OBJECTIVE: To study the level of serum calcium and the method of calcium supplement in newborns with hypoxic ischemic encephalopathy (HIE) accompanied by hypocalcemia. METHODS: Sixty four neonates with HIE accompanied by hypocalcemia were randomly assigned into the treatment group (n=32) and control group (n=32). The treatment group received calcium supplement immediately after hospitalization, and the control group at the second week after hospitalization. The serum calcium level was estimated in the two groups on admission, the seventh day and fourteenth day respectively.RESULTS: Serum free calcium levels were ( 0.78 ± 0.10 ), ( 0.72 ± 0.13 ) and ( 0.56 ± 0.09 ) mmo1/L, respectively, in the 18 cases with mild HIE, 30 cases with moderate HIE and 16 cases with severe HIE. There was no difference between the mild cases and the moderate cases, while significant difference was found between the severe cases and mild cases or the moderate cases (both P< 0.01 ). The serum free calcium level at admission and on the fourteenth day in the two groups was not different; but the serum free calcicum of the seventh day in the treatment group was obviously higher than that in the control group (P< 0.01 ). CONCLUSIONS: Supplementing calcium routinely was safe in HIE neonates with a lower serum free calcium level. The prognosis will not be influenced by the timing of calcium supplement.